// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_H_
#define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_H_

#include <map>
#include <memory>
#include <string>

#include "base/files/file_path.h"
#include "base/gtest_prod_util.h"
#include "base/strings/nullable_string16.h"
#include "base/strings/string16.h"
#include "content/common/content_export.h"
#include "content/common/dom_storage/dom_storage_types.h"
#include "sql/connection.h"

namespace base {
namespace trace_event {
    class ProcessMemoryDump;
}
}

namespace content {

// Represents a SQLite based backing for DOM storage data. This
// class is designed to be used on a single thread.
class CONTENT_EXPORT DOMStorageDatabase {
public:
    static base::FilePath GetJournalFilePath(const base::FilePath& database_path);

    explicit DOMStorageDatabase(const base::FilePath& file_path);
    virtual ~DOMStorageDatabase(); // virtual for unit testing

    // Reads all the key, value pairs stored in the database and returns
    // them. |result| is assumed to be empty and any duplicate keys will
    // be overwritten. If the database exists on disk then it will be
    // opened. If it does not exist then it will not be created and
    // |result| will be unmodified.
    void ReadAllValues(DOMStorageValuesMap* result);

    // Updates the backing database. Will remove all keys before updating
    // the database if |clear_all_first| is set. Then all entries in
    // |changes| will be examined - keys mapped to a null NullableString16
    // will be removed and all others will be inserted/updated as appropriate.
    bool CommitChanges(bool clear_all_first, const DOMStorageValuesMap& changes);

    // Adds memory statistics of the database to |pmd| for tracing.
    void ReportMemoryUsage(base::trace_event::ProcessMemoryDump* pmd,
        const std::string& name);

    // Simple getter for the path we were constructed with.
    const base::FilePath& file_path() const { return file_path_; }

protected:
    // Constructor that uses an in-memory sqlite database, for testing.
    DOMStorageDatabase();

private:
    friend class LocalStorageDatabaseAdapter;
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, SimpleOpenAndClose);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, TestLazyOpenIsLazy);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, TestDetectSchemaVersion);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest,
        TestLazyOpenUpgradesDatabase);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, SimpleWriteAndReadBack);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, WriteWithClear);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest,
        UpgradeFromV1ToV2WithData);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest, TestSimpleRemoveOneValue);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest,
        TestCanOpenAndReadWebCoreDatabase);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageDatabaseTest,
        TestCanOpenFileThatIsNotADatabase);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, BackingDatabaseOpened);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, CommitTasks);
    FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, PurgeMemory);

    enum SchemaVersion {
        INVALID,
        V1,
        V2
    };

    // Open the database at file_path_ if it exists already and creates it if
    // |create_if_needed| is true.
    // Ensures we are at the correct database version and creates or updates
    // tables as necessary. Returns false on failure.
    bool LazyOpen(bool create_if_needed);

    // Analyses the database to verify that the connection that is open is indeed
    // a valid database and works out the schema version.
    SchemaVersion DetectSchemaVersion();

    // Creates the database table at V2. Returns true if the table was created
    // successfully, false otherwise. Will return false if the table already
    // exists.
    bool CreateTableV2();

    // If we have issues while trying to open the file (corrupted databse,
    // failing to upgrade, that sort of thing) this function will remove
    // the file from disk and attempt to create a new database from
    // scratch.
    bool DeleteFileAndRecreate();

    // Version 1 -> 2 migrates the value column in the ItemTable from a TEXT
    // to a BLOB. Exisitng data is preserved on success. Returns false if the
    // upgrade failed. If true is returned, the database is guaranteed to be at
    // version 2.
    bool UpgradeVersion1To2();

    void Close();
    bool IsOpen() const { return db_.get() ? db_->is_open() : false; }

    // Initialization code shared between the two constructors of this class.
    void Init();

    // Path to the database on disk.
    const base::FilePath file_path_;
    std::unique_ptr<sql::Connection> db_;
    bool failed_to_open_;
    bool tried_to_recreate_;
    bool known_to_be_empty_;
};

} // namespace content

#endif // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_H_
